DISCOVERY EDUCATION SCIENCE CONNECTION

certain multicelled organisms that get tostay in one place and make their food, I haveto go out and get my chow myself.

Q: Which multicelled organisms are youtalking about?

A: Plants. You know, the green things thatstay in the same spot their whole lives? Plantshave it made. Every time the Sun shines, thedinner bell rings.

Q: How so?

A: Plants don’t have to go anywhere to gettheir food. That’s what being planted means:staying in one place. Even plants that “creep,”like vines, are rooted in one place that doesn’tchange. The point is, everything plants needto make food is either built into their cells oralways within reach. They take in carbondioxide from the air. They slurp water out ofthe ground. Then sunlight helps to change itall into food right in their own leaf cells. It’snot fair.

Q: You’re an amoeba, composed of only onecell. A kind of shapeless cell, if I may.

A: No, you may not. I happen to like myshape very much. And besides, I can change itany time I want, and fast (well, more or less).

Q: Well, yes, but no matter what you do, anamoeba’s shape is still kind of blob-like.Maybe you should consider getting moreexercise. Firm up that jelly-like stuff a bit.

A: MORE exercise? I spend my lifeexercising. That’s all I do. Only I prefer to callit work. Hard work.

Q: Hard work? How can something thatlooks so soft and squishy work hard?

A: Because all cells have to have foodenergy—yours, mine, an artichoke’s. And inmy case, eating means I have to move. Hunt.Sneak up on some unsuspecting piece ofpond scum or clueless bacterium. Unlike

Interview with an amoeba

Gotta Split

Q: But it sounds like a good trick. Canpeople learn to do that? Manufacture foodright in their cells?

A: Nope, but that’s why humans createdsupermarkets, take-out pizzas, and lots ofother food suppliers. Each person has aboutfifty to a hundred million million cells. That’sa lot to feed. You need a lot of food. You alsoneed something else.

Q: What?

A: A mouth. The first stop on the road toeach and every individual cell in your body.Of course, that’s only the beginning. Foodneeds to get mashed and strained and pushedthrough your digestive system before it canreach your cells.

Q: Once it gets there, how does the foodactually get inside our cells ?

A: One word: membrane. That’s the layer onthe outside of a cell. All cells have them. Me,too! Membranes are designed so thatnutrients can move in and wastes can go out.That’s how your cells get fed and that’s howmy cell—which you can also call my “self”—gets fed. I love my membrane. I use it in areally special way.

Q: Which is?

A: Since it’s nice and flexible, I can fold it allaround the bacterium (or alga or whatever ismy menu of the moment) and then pull myprey inside me whole. Then I digest the parts I want and push the waste out later.

Q: How often do you do this foldingand eating thing?

A: Constantly. Never stop. Love to eat.Live to eat. I eat and eat and eat until I’vedoubled my size. And then somethingwonderful happens.

Q: What is it?

A: I divide into two brand-new cells. That’smy purpose in life—making more of me.Making two independent-minded, free-thinking, wonderful one-celled creatures wherethere was just one. It all happens in only abouta day—just twenty-four hours.

Q: Pretty impressive. Do all living thingsreproduce like you?

A: Nope. All cells have to divide for theirorganisms to grow. But a multicelledorganism needs a partner to reproduce. Wesolo cells only need ourselves. Our type ofreproduction is asexual, and it’s called binaryfission. Speaking of which, we’d better wrapthis up. I need to split in a few minutes.

Q: OK. Last question. When all’s said anddone, would you ever want to trade thestressful life of a short-lived, constantlyhunting one-celled organism for the slower-paced life of a multicelled creature? Say, ahuman being?

A: No way. I like things the way they are: justme, myself, and I. No complicated organs andsystems and such. Give me the simple life.And I have lots of company. There are waymore one-celled organisms in the world thanmulticelled ones. My ancestors were here atthe beginning of life on Earth, or at least along time ago. Who knows? Someday wemight just be the only ones left.

IN AND OUT An amoeba’s form is bounded by itsmembrane. The membrane shape changes as thematerials inside the amoeba shift around and push againstthe membrane. The main ingredient inside a cell is water.A main ingredient of a cell’s membrane is a layer of lipids,or fats. The layer of fat provides a clear boundary from thewater. To see how this works, fill a glass about halfwaywith water, and add a drop of food coloring to the water.Then add about half a cup of cooking oil, such as olive oilor vegetable oil. Stir the mixture vigorously and then letthe contents settle. Write down your observations.

DISCOVERY EDUCATION SCIENCE CONNECTION